The present invention relates to a color liquid crystal display and, particularly, to a color liquid crystal display which has high display qualities and is highly reliable.
In recent years, color liquid crystal displays have attracted remarkable attention as flat displays. One example of these color liquid crystal displays has a schematic structure comprising a color filter substrate including a black matrix, a colored layer consisting of plural colors (three primary colors: red (R), green (G) and blue (B)), a transparent electrode and an oriented layer, a counter electrode substrate including a thin film transistor (TFT element), a pixel electrode and an oriented layer, and a liquid crystal layer formed by opposing these both substrates to each other with a predetermined gap between them, sealing by a sealing member and filling a liquid crystal material in the gap.
In such a color liquid crystal display, the aforementioned gap is just the thickness of the liquid crystal. The thickness of the above liquid crystal layer, namely the distance between the color filter substrate and the counter electrode substrate must be kept strictly constant to enable exhibition of high display efficiencies which is required to a color liquid crystal display, including high speed responsibility, high contrast ration and wide angle of view. This is the reason why the following settings are taken. Specifically, before the color filter substrate and the counter electrode substrate are applied to each other, glass beads or plastic beads with a predetermined diameter and uniform grain diameter are dispersed as a spacer in either one of the color filter substrate and the counter electrode substrate. Thereafter, both substrates are applied to each other and sealed by a sealing member. Thus, the distance of the gap between both substrates, namely the thickness of the liquid crystal layer is set corresponding to the diameter of the glass beads or plastic beads.
However, because a curable synthetic resin is usually used as the sealing member, the generation of reaction gas and the elution of a solvent are caused in a curing process after the color filter substrate and the counter electrode substrate are applied to each other and sealed. There is the case where the liquid crystal layer is thereby contaminated and hence produces display nonuniformity, leading to reduced display qualities.
In order to solve such a problem, a color liquid crystal display is proposed in which an organic film is formed inside of the sealing member to prevent the liquid crystal layer from being contaminated with the reaction gas and eluents from the sealing member (Japanese Patent Application Laid-Open (JP-A) No. H8-328024).
However, when the organic film itself contains substances which contaminate the liquid crystal layer, the problem, such as the aforementioned display nonuniformity, which deteriorates the display qualities of the liquid crystal layer cannot be solved.
Also, in such a color liquid crystal display as mentioned above, a step of forming the organic film by a photolithographic method is required in addition to a step of forming the colored layer comprising the black matrix and three colors of R, G and B. This poses the problems of, for example, complicated steps and reduced throughput and yield. Moreover, in the case of using glass beads or plastic beads as a spacer as aforementioned, there is the case where the thickness of the liquid crystal layer is not formed uniformly and the orientation of liquid crystal molecules is disordered when the distribution of the spacer is nonuniform and the spacer are present on display pixels, giving rise to the problem of a reduction in the display efficiencies including contrast ration.
The present invention has been made in view of the above problems and has an object of providing a color liquid crystal display which is provided with a shielding member disposed between a sealing member and a display zone to prevent the liquid crystal layer from being contaminated with liquid crystal layer-contaminants from the sealing member wherein the above shielding member is formed of a material excluding substances, which adversely affect the liquid crystal layer, and/or can be produced in a simple production process.
The above object can be attained by the following color liquid crystal display of the present invention. According to the first aspect of the present invention, there is provided a color liquid crystal display comprising at least a color filter substrate provided with a colored layer with plural colors formed into a predetermined pattern in a display zone on a transparent substrate, a counter electrode substrate disposed opposite to and with a predetermined gap from the color filter substrate, a sealing member disposed outside of the display zone to seal the gap formed between both substrates, a liquid crystal layer formed by filling a liquid crystal material in the gap formed between both substrates and sealed by the sealing member and a shielding member disposed between the sealing member and the display zone to prevent the liquid crystal material contained in the liquid crystal layer from being contaminated with contaminants from the sealing member, the shielding member being formed of a material which works such that the voltage retention and residual DC (xcex94E) of the liquid crystal material after the impurity-extraction treatment is 80% or more and 0.5 V or less respectively.
The color liquid crystal display of the present invention is provided with the shielding member disposed between the sealing member and the display zone in this manner. Hence the liquid crystal material of the liquid crystal layer never be contaminated with contaminants from the sealing member. Moreover, because the shielding member is formed of such a material as aforementioned, the contamination of the liquid crystal material which is caused by the material of the shielding member is prevented, decreasing the possibilities of white unevenness and seizure of the liquid crystal.
In one form of the color liquid crystal display according to the first aspect of the present invention, preferably the shielding member is formed of a material which does not contain pigments, pigment derivatives, dyes or dye derivatives. This is because these pigments, pigment derivatives, dyes or dye derivatives contaminate the liquid crystal material highly possibly though it depends upon the types of these materials and hence there is the case where the shielding member cannot work such that the voltage retention of the liquid crystal material is 80% or more and the residual DC (xcex94E) of the liquid crystal material is 0.5 V or less when the liquid crystal material is subjected to impurity-extraction treatment using a material containing a pigment or pigment derivative or a dye or dye derivative.
According to the second aspect of the present invention, there is provided a color liquid crystal display comprising at least a color filter substrate provided with a colored layer with plural colors formed into a predetermined pattern in a display zone on a transparent substrate, a counter electrode substrate disposed opposite to and with a predetermined gap from the color filter substrate, a sealing member disposed outside of the display zone to seal the gap formed between both substrates, a liquid crystal layer formed by filling a liquid crystal material in the gap formed between both substrates and sealed by the sealing member, a columnar convex portion formed so as to keep the gap between both substrates constant and a shielding member disposed between the sealing member and the display zone to prevent the liquid crystal material of the liquid crystal layer from being contaminated with contaminants from the sealing member and formed of the same material as the columnar convex portion.
Since the material of the shielding member is formed of the same material as the columnar convex portion like this, the shielding member can be produced at the same time when the columnar convex portion is formed. Accordingly, no additional photolithographic step only for producing the shielding member is not required and a color liquid crystal display having a shielding member can be thereby produced in a simple production process. Also, the columnar convex portion which serves to uniform the gap between both substrates can be produced at the same time when the shielding member is produced. It is therefore unnecessary to use glass beads or plastic beads as a spacer. This prevents the production of disorders, namely uneven thickness of the liquid crystal layer and disordered orientation of liquid crystal molecules owing to ununiform dispersion of the spacer and the presence of the spacer on the display pixels, which are produced when such a spacer is used. The display performance such as contrast ration is not decreased resultantly.
In one form of the color liquid crystal display according to the second aspect of the present invention, preferably the shielding member is formed of a material which works such that the voltage retention and residual DC (xcex94E) of the liquid crystal material after the impurity-extraction treatment is 80% or more and 0.5 V or less respectively. This makes it possible to produce a color liquid crystal display having both advantages of the color liquid crystal displays according to the first and second aspects of the present invention.
In another form of the color liquid crystal display according to the second aspect of the present invention, preferably the shielding member is formed of the same material as the columnar convex portion and a protective layer. This is because when the shielding member, the columnar convex portion and the protective layer are formed of the same materials in this manner, the three can be formed in one step simultaneously and hence the step of producing the color liquid crystal display can be simplified, which can reduce production costs.
In a further form of the color liquid crystal display according to the second aspect of the present invention, preferably at least a part of the shielding member is formed on a black matrix disposed outside of the display zone.
The formation of a part or all of the shielding member formed on the black matrix disposed outside of the display zone causes the formation of a clearance between the shielding member and the either one of substrates. Specifically, when the shielding member and the columnar convex portion are formed at the same time, the shielding member has the same height as the columnar convex portion. Since the columnar convex portion is formed on the colored layer, the altitude of the columnar convex portion from the substrate surface is higher than that of the shielding member formed on the black matrix by the difference in thickness between the colored layer and the black matrix. Because the gap between the color filter substrate and the counter electrode substrate is defined by the altitude of the columnar convex portion, the clearance is formed between the shielding member and the substrate resultantly.
By forming such a clearance between the shielding member and the substrate, a liquid crystal can be flowed into the clearance between the shielding member and the sealing member when the liquid crystal is filled in the gap between the both substrates. This offers the advantage that the air present between the shielding member and the sealing member is prevented from intruding into the liquid crystal layer. It is to be noted that since the clearance is very small, liquid crystal material-contaminants from the sealing member will not leak from the clearance much enough to produce an adverse effect on the liquid crystal material.
In a still further form of the color liquid crystal display according to the second aspect of the present invention, preferably at least a part of the shielding member is formed on at least one dummy colored layer formed on the black matrix disposed outside of the display zone.
If a part or all of the shielding member is formed on at least one dummy colored layer formed on the black matrix, the shielding member has the same altitude as or slightly higher altitude than that of the columnar convex portion when the shielding member and the columnar convex portion are formed at the same time. It is therefore possible to use the shielding member, like the columnar convex portion, as the spacer which serves to keep a predetermined gap between both substrates. This structure is also useful particularly when it is intended to prevent the sealing member perfectly from being in contact with the liquid crystal material.
In a further version of the color liquid crystal display according to the second aspect of the present invention, preferably the shielding member in the vicinity of a liquid crystal-sealing port and/or a straightening vane of a liquid crystal-sealing port is produced by forming a convex portion formed of the same material as the columnar convex portion on at least one dummy colored layer formed on the black matrix.
When the gap between both substrates at the liquid crystal-sealing port is small, there is the case where the filling rate of the liquid crystal is made slow, giving rise to an efficiency problem. Therefore, a predetermined gap size must be kept between both substrates at the sealing port. The reason why the shielding member in the vicinity of the sealing port and/or the straightening vane of the sealing port is structured by forming a convex portion formed of the same material as the columnar convex portion on at least one dummy colored layer as aforementioned is that the liquid crystal material-sealing port is prevented from being made narrower, which can avoid disorders such as a reduction in the filling rate of the liquid crystal and allows the production of the display in a simpler process.
In a still further version of the color liquid crystal display according to the present invention, preferably the shielding member is formed on a transparent electrode. When the shielding member is formed on a transparent electrode in this manner, the transparent electrode can be led out of the sealing member with ease thereby wiring easily. When the transparent electrode is laid on the shielding member, there is the case where it is necessary to form an insulated layer on the opposite substrate. In this case, a predetermined width is required in light of accuracy. If the shielding member is formed on the transparent electrode, it is unnecessary to form the insulated layer on the opposite substrate and hence a narrow architrave configuration can be attained.